1. Field of the Invention
The present invention generally relates to a method for achieving uniform expansion of a dielectric plate and a dielectric plate made thereby.
2. The Prior Art
A central processing unit (CPU) of a computer is mounted to a main computer board by means of a connector. Conventionally, the CPU connector has contacts extending beyond top and bottom faces thereof for electrical engagement with pins of the CPU and conductive traces of the main board. The contacts are soldered to the main board by a through hole technique. Such a connector structure occupies a substantial amount of space on the main board and requires a sophisticated process to mount the connector thereon.
A ball grid array (BGA) connector effectively overcomes the problems discussed above. As shown in FIG. 3 of the attached drawings, a BGA connector 4 comprises a dielectric base plate 40 defining a number of bores (not labeled) therein between top and bottom faces thereof for receiving and retaining conductive contacts 41. Each contact 41 has a solder support section 42 extending beyond the bottom face of the base plate 40. A solder ball 3 is attached to the solder support section 42 by preheating the solder support section 42.
The contacts 41 are aligned with contact pads 50 formed on a circuit board 5 whereby when the base plate 40 is properly positioned on the circuit board 5, the solder balls 3 contact the corresponding contact pads 50. By means of heating, the solder balls 3 become molten and then solidify to be fixed to the contact pads 50 of the circuit board 5. An efficient and effective method for soldering the connector 4 to the circuit board 5 is thus achieved.
However, since the base plate 40 of the connector 4 and the circuit board 5 are generally made of different material having different thermal expansion coefficients, heating the solder balls 3 to fix the contacts 41 to the contact pads 50 will result in different amounts of expansion between the circuit board 5 and the base plate 40 leading to an undesired strain on the solder balls 3.
Furthermore, the base plate 40 is usually made by means of injection molding. During the molding process, plasticized dielectric material flows into a mold. Due to the complicated configuration of the base, a non-uniform distribution of the molecules of the dielectric material results leading to different amounts of thermal expansion in different directions of the base plate 40 when the base plate 40 is heated during a BGA soldering process. Such nonuniform thermal properties further complicate the above-mentioned problem.
Thus, it is desired to provide a method for achieving uniform expansion of a dielectric plate.